Currently, if an Image source has a certain Extent, Paraview will pass that as UPDATE_EXTENT to all subsequent filters in the pipeline, even if a filter changes the whole extent. This prohibits for example implementing vtkImageConstantPad as a useful Paraview filter. For further info see http://markmail.org/message/sfnw7sgojytzw6y2 [^] .

I am sure this has something to do with the fact that ParaView uses its own extent translator that uses the reader's extents.

It prohibits the use of every filter that has output extent larger than input extent. vtkImagePadFilters'children have, but vtkImageReslice and children are also affected. It also prevents the implementation of filters that have totally independent output extent, such as an orthogonal reslicing along a spline curve.

IMHO, the severity is higher than 'minor': FFT filtering is not possible in ParaView !!